Device and method for controlling working state change of small cell

ABSTRACT

A device and method controlling working state change of a small cell and a base station including the device. The device includes: an information acquiring unit that acquires interference between a small cell to be controlled and an adjacent small cell and/or load of the small cell to be controlled; and a state change determination unit that determines working state change to be performed by the small cell to be controlled according to the acquired interference and/or load. The working state includes multiple sleep levels from low to high. A sleep degree of the small cell to be controlled in a low sleep level is less than a sleep degree of the small cell to be controlled in a high sleep level, the working state change being performed among multiple sleep levels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/102,441, filed on Jun. 7, 2016, which is based on National StageApplication PCT/CN2014/094652, filed on Dec. 23, 2014, which claims thebenefit of priority of the Chinese Patent Application No.201310737660.3, filed with the Chinese State Intellectual PropertyOffice on Dec. 26, 2013, the entire disclosure of which is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention generally relates to the field of wirelesscommunications, and particularly relates to the advanced long termevolution (LTE-A) technique. More particularly, the present inventionrelates to an apparatus and method for controlling a change of operationstate of a small cell, with respect to the requirement of the criticaltechniques of LTE-A based on the setting of cells in 3GPP Release 12.

BACKGROUND OF THE INVENTION

LTE is a long term evolution of the technique standard of the UniversalMobile Telecommunications System (UMTS) established by the 3rdGeneration Partnership Project (3GPP) organization, and is approvedregularly and started in the meeting of 3GPP TSG RAN #26 in December,2004, in Toronto. An LTE system introduces critical transmissiontechniques such as Orthogonal Frequency Division Multiplexing (OFDM) andMultiple-Input Multiple-Output (MIMO) of multiple antennas, andincreases the spectrum efficiency and data transmission ratesignificantly. The peak data rate can reach 50 Mbit/s for uplink and 100Mbit/s for downlink. Further, the system supports various distributionof bandwidth, and thus the distribution of spectrum is more flexible,with the capacity and coverage of the system significantly increased.The architecture of the LTE wireless networks is more flattened,reducing the system delay and reducing the costs for network buildingand maintaining.

In addition, in LTE-A, in order to acquire sufficient transmissionbandwidth (such as 100 MHz) to support higher uplink and downlink peakdata rate (such as 1 Gbit/s for downlink and 500 Mbit/s for uplink), thecarrier aggregation technique can be adopted to aggregate a plurality ofcomponent carriers to obtain high bandwidth transmission.

In LTE R12, small cells are introduced. A small cell is a wirelessaccess node with low power, operates in an unlicensed or licensedspectrum, and can cover a range of 10 m to 200 m. In contrast, thecoverage range of a macro cell can reach as much as several kilometers.The small cell fuses techniques of femtocell, picocell, microcell anddistributed wireless techniques. The small cell has a very small volumeand can be used indoor and outdoor. Generally, the small cell can coverthe indoor space of about 10 m or a range of 2 kilometers in the openair. As shown in FIG. 1, where the multiple smaller circles representsmall cells and the three relatively larger circles represent macrocells, it can be seen that the small cells are characterized in thatthey are densely arranged with the coverage ranges crossed with eachother. In the scenario of LTE-A heterogeneous networks, the macro cellsrealize wide area coverage and the small cells realize Hotpointcoverage.

Considering that a large amount of small cells would appear in thefuture applications, it becomes more important to enable more effectiveutilization of energy and network resources in the networks. Of course,it is also necessary to guarantee the communication quality of the userterminals accessing into the cells. The “cells” in the context includesboth macro cells and small cells if not specified otherwise.

SUMMARY OF THE INVENTION

In the following, an overview of the present invention is given simplyto provide basic understanding to some aspects of the present invention.It should be understood that this overview is not an exhaustive overviewof the present invention. It is not intended to determine a criticalpart or an important part of the present invention, nor to limit thescope of the present invention. An object of the overview is only togive some concepts in a simplified manner, which serves as a preface ofa more detailed description described later.

In view of the above demand, the present application aims to provide atechnical solution which reduces the energy consumption of each cell asmuch as possible while guaranteeing the communication quality.Specifically, a small cell to be controlled is caused to sleep indifferent levels, according to the interference degree between the smallcell to be controlled and an adjacent small cell, and/or load of thesmall cell to be controlled or load to be distributed to the small cell,so as to reduce unnecessary energy consumption. Since the macro cell isgenerally not allowed to sleep, the controlling object herein is thesmall cell.

According to an aspect of the present invention, an apparatus forcontrolling a change of operation state of a small cell is provided,including: an information acquiring unit, configured to acquireinterferences between the small cell to be controlled and an adjacentsmall cell, and/or load of the small cell to be controlled or load to betaken on by the small cell to be controlled which is distributed byother cells; and a state change determining unit, configured todetermine, based on the interferences and/or the load acquired by theinformation acquiring unit, a change of operation state to be performedby the small cell to be controlled, wherein, the operation stateincludes multiple sleep levels from low to high, and the small cell tobe controlled has a lighter degree of sleep when it is at a lower sleeplevel than when it is at a higher sleep level, the change of operationstate being performed among the multiple sleep levels.

According to another aspect of the present invention, an apparatus forchanging an operation state of a small cell is provided, including: acontrol signal receiving unit, configured to receive a control signalfrom the above mentioned apparatus for controlling; and a state changingunit, configured to change, based on the control signal, the operationstate of the small cell.

According to still another aspect of the present invention, a basestation is further provided, including one of the two kinds of apparatusmentioned above.

According to an aspect of the present invention, a method forcontrolling a change of operation state of a small cell is provided,including: acquiring interferences between the small cell to becontrolled and an adjacent small cell, and/or load of the small cell tobe controlled or load to be taken on by the small cell to be controlledwhich is distributed by other cells; and determining, based on theacquired interferences and/or the load, a change of operation state tobe performed by the small cell to be controlled, wherein, the operationstate includes multiple sleep levels from low to high, and the smallcell to be controlled has a lighter degree of sleep when it is at alower sleep level than when it is at a higher sleep level, the change ofoperation state being performed among the multiple sleep levels.

According to other aspects of the present invention, there are furtherprovided computer program codes and computer program product forimplementing the above mentioned method for controlling a change ofoperation state of a small cell, as well as a computer readable storagemedium on which computer program codes for realizing the aforementionedmethod for controlling a change of operation state of a small cell arerecorded.

The method for controlling a change of operation state of a small cellof the present application is capable of changing a sleep level of thesmall cell appropriately according to the interference and/or loadstatus of the small cell, thereby reducing the energy consumption whilemaking use of the network resources effectively.

These and other advantages of the present invention will be moreapparent by illustrating in detail a preferred embodiment of the presentinvention in conjunction with accompanying drawings below.

BRIEF DESCRIPTION OF THE DRAWINGS

To further set forth the above and other advantages and features of thepresent invention, detailed description will be made in the followingtaken in conjunction with accompanying drawings in which identical orlike reference signs designate identical or like components. Theaccompanying drawings, together with the detailed description below, areincorporated into and form a part of the specification. It should benoted that the accompanying drawings only illustrate, by way of example,typical embodiments of the present invention and should not be construedas a limitation to the scope of the invention. In the accompanyingdrawings:

FIG. 1 is a schematic drawing illustrating the spatial distribution inan example of the application scenario including macro cells and smallcells;

FIG. 2 is a structural block diagram of the apparatus for controlling achange of operation state of a small cell according to an embodiment ofthe present application;

FIG. 3 is a schematic drawing illustrating the sleep levels according toan embodiment of the present application;

FIG. 4 is a schematic drawing illustrating an example of an applicationscenario including a macro cell, a small cell to be controlled and itsadjacent small cells, and user terminals (UE) in the small cells;

FIG. 5 is a structural block diagram of the information acquiring unitaccording to an embodiment of the present application;

FIG. 6 is a diagram illustrating an example for calculating the distanced1 between the user terminal UEa and the base station T of the smallcell to be controlled;

FIG. 7 shows a schematic timing chart for the signal transmitting andreceiving among the small cell base stations T, N and the user terminalUEa in FIG. 6;

FIG. 8 is a structural block diagram of the information acquiring unitaccording to another embodiment of the present application;

FIG. 9 is a structural block diagram of the information acquiring unitaccording to still another embodiment of the present application;

FIG. 10 is a structural block diagram of the apparatus for controlling achange of operation state of a small cell according to anotherembodiment of the present application;

FIG. 11 is a structural block diagram of the apparatus for controlling achange of operation state of a small cell according to still anotherembodiment of the present application;

FIG. 12 is a structural block diagram of the apparatus for controlling achange of operation state of a small cell according to anotherembodiment of the present application;

FIG. 13 is a structural block diagram of the apparatus for changing theoperation state of a small cell according to an embodiment of thepresent application;

FIG. 14 is a structural block diagram of the apparatus for changing theoperation state of a small cell according to another embodiment of thepresent application;

FIG. 15 is a structural block diagram of the apparatus for changing theoperation state of a small cell according to still another embodiment ofthe present application;

FIG. 16 is a flowchart illustrating the method for controlling a changeof operation state of a small cell according to embodiments of thepresent application;

FIG. 17 is a flowchart illustrating an example of sub-steps of the stepS11 in FIG. 16;

FIG. 18 is a flowchart illustrating another example of sub-steps of thestep S11 in FIG. 16;

FIG. 19 is a flowchart illustrating the method for changing theoperation state of a small cell;

FIG. 20 shows the interference list in an system instance;

FIG. 21 shows another interference list in an system instance; and

FIG. 22 is an exemplary block diagram illustrating the structure of ageneral purpose personal computer capable of realizing the method and/orapparatus and/or system according to the embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of the present invention will be describedhereinafter in conjunction with the accompanying drawings. For thepurpose of conciseness and clarity, not all features of an embodimentare described in this specification. However, it should be understoodthat multiple decisions specific to the embodiment have to be made in aprocess of developing any such embodiment to realize a particular objectof a developer, for example, conforming to those constraints related toa system and a business, and these constraints may change as theembodiments differs. Furthermore, it should also be understood thatalthough the development work may be very complicated andtime-consuming, for those skilled in the art benefiting from the presentdisclosure, such development work is only a routine task.

Here, it should also be noted that in order to avoid obscuring thepresent invention due to unnecessary details, only a device structureand/or processing steps closely related to the solution according to thepresent invention are illustrated in the accompanying drawing, and otherdetails having little relationship to the present invention are omitted.

The First Embodiment

FIG. 2 illustrates an apparatus 100 for controlling a change ofoperation state of a small cell according to an embodiment of thepresent application. As shown in FIG. 2, the apparatus 100 includes: aninformation acquiring unit 101, configured to acquire interferencesbetween the small cell to be controlled and an adjacent small cell,and/or load of the small cell to be controlled or load to be taken on bythe small cell to be controlled which is distributed by other cells; anda state change determining unit 102, configured to determine, based onthe interferences and/or the load acquired by the information acquiringunit, a change of operation state to be performed by the small cell tobe controlled, wherein, the operation state includes multiple sleeplevels from low to high, and the small cell to be controlled has alighter degree of sleep when it is at a lower sleep level than when itis at a higher sleep level, the change of operation state beingperformed among the multiple sleep levels.

Specifically, the information acquiring unit 101 can acquire informationabout two aspects of both the interference and the load or only acquireinformation about one of the aspects, and provide the acquiredinformation to the state change determining unit 102, so that the statechange determining unit 102 is capable of determining, based on theinformation, whether to change the operation state of the small cell oreven how to change the operation state of the small cell, such asturning off or turning on a part of the function of its base station,i.e., sleeping in different degrees. The interferences between the smallcell to be controlled and the adjacent small cell are mutual. That is,they include both the interferences the small cell to be controlledproduces to the adjacent small cell and the interferences the adjacentsmall cell produces to the small cell to be controlled.

The information acquiring unit 101 can acquire the above mentionedinformation by directly detecting the small cell to be controlled in thecontrolling range of the apparatus 100. Alternatively, it can also bethe case that each small cell to be controlled detects respectively andreports the detected information to the information acquiring unit 101.The information about the interference and/or load can be various, andwill be described in detail in the following embodiments. Depending onthe type and content of the information, the state change determiningunit 102 determines the change of operation state to be performed, i.e.,the change of sleep of level to be performed, correspondingly.

In the apparatus 100, multiple sleep levels can be set. The lower thesleep level is, the more active the small cell is indicated to be, andthe larger the ratio of the function of the base station of the smallcell being turned on accounts for. Otherwise, the higher the sleep levelis, the smaller the ratio of the function of the base station of thesmall cell being turned on accounts for.

In an example, the sleep levels include: small cell base station wakingup completely, sub-frame sleep, sub-carrier downlink sleep, sub-carrieruplink and downlink sleep, small cell base station downlink sleep andsmall cell base station uplink and downlink sleep. As shown in FIG. 3,the sleep level is increased step by step from the small cell basestation waking up completely to the small cell base station uplink anddownlink sleep.

Wherein, the small cell base station waking up completely means that allsub-frames on all carriers of the base station of small cell are turnedon, the sub-frame sleep means that a part of sub-frames on the carriersbeing turned on are turned off, the sub-carrier downlink sleep meansthat all the downlink sub-frames on a part of carriers of the basestation of the small cell are turned off, the sub-carrier uplink anddownlink sleep means that all the uplink sub-frames and downlinksub-frames on a part of carriers of the base station of the small cellare turned off, the small cell base station downlink sleep means thatall the downlink sub-frames of the base station of the small cell areturned off, and the small cell base station uplink and downlink sleepmeans that all the uplink sub-frames and downlink sub-frames of the basestation of the small cell are turned off, i.e., turning off the smallcell completely. It can be seen that the higher the sleep level of thesmall cell is, the less its consumed energy is.

In this level setting, the downlink is turned off first in contrast withthe uplink. For example, as for the levels of sub-carrier downlink sleepand small cell base station downlink sleep, the downlink is turned offwhile the uplink remains. For example, as for the small cell basestation downlink sleep, on the carriers of the small cell, there is nodata communication between the user and the base station. That is, thebase station does not transmit information to the user, while the userdoes not transmit information to the base station as well. However,since the user may transmit the uplink signal such as PRACH or SRS whenaccessing into other carriers or other cells, the small cell, which isin a state of the small cell base station downlink sleep with the uplinkbeing turned on, can detect the uplink signal of the user. The uplinksignal can be used as basis for various measurements and judgments, suchas the signal to interference and noise ratio (SINR) measurement of theuser and the judgment of the high-interference user terminal.

Therefore, compared with turning off both uplink and downlink, justturning on the uplink while turning off the downlink facilitates thedetection of information such as the load and interference within thefrequency band by the base station. If both the uplink and the downlinkare turned off, it means that the carrier or the small cell no longerdetects information of the user terminal. Therefore, the state ofturning off the downlink while turning on the uplink can function as atransition state between the full on and the full off, which is used fordetecting the operation state of the user terminals in its frequencyband.

Although six sleep levels are illustrated herein as an example, thedivision of the sleep levels is not limited thereto. Instead, variousother dividing manners can be adopted. For example, in order to reducethe system complexity, three levels or four levels can be used: smallcell base station waking up completely, sub-frame sleep, sub-carriersleep and small cell base station sleep; or small cell base stationwaking up completely, small cell base station downlink sleep, and smallcell base station uplink and downlink sleep. If the number of levelsbecomes more, the granularity for controlling can be finer.

The apparatus 100 can be a separate controlling apparatus, and can alsobe a controlling apparatus located in the base station of a small cellserving as the cluster header or in the base station of a macro cell.The apparatus 100 can control multiple small cells. Further, theapparatus 100 can be located in the base station of each small cell, fordetermining the change of operation state to be performed by the smallcell which it is located in.

In the case that the apparatus 100 is a separate controlling apparatusor located in the base station of a small cell serving as the clusterheader or in the base station of a macro cell, the apparatus 100 canfurther include a transmitting unit, configured to transmit the changeof operation state determined by the state change determining unit 102as a control signal to the small cell to be controlled, so as to controlit to perform the change of operation state. In such a situation, theapparatus 100 plays the role of a central controller, and manages theoperation state of the multiple small cells in its coverage range.

The Second Embodiment

In the small cell distribution scenario shown in FIG. 1 where there aremultiple small cells, one of the small cells may produce interference toanother adjacent small cell, and the apparatus 100 can judge the changeof operation state of this small cell to be performed according to adegree of the interference.

FIG. 4 illustrates the diagram of an example of an application scenarioincluding a macro cell, a small cell to be controlled and the adjacentsmall cells thereof, as well as the user terminals (UEs) in the smallcells. It is to be understood that FIG. 4 is only an example for thepurpose of facilitating the understanding of the present application,and the scenarios where the present invention can be applied are notlimited thereto.

In an example, the information acquiring unit 101 is configured toacquire the number of high-interference user terminals in the adjacentsmall cell to determine a degree of interference the small cell to becontrolled produced to the adjacent small cell, wherein, theinterferences the high-interference user terminal being subjected tofrom the small cell to be controlled exceed a predetermined limit. Here,the number of the high-interference UEs can be used directly as a valueof the degree of interference. It is also possible to map the differentnumbers of the high-interference UEs to respective level of the degreeof interference.

Herein, the information acquiring unit 101 can detect the number of thehigh-interference UEs by itself, or receive a report about this numberfrom the base station of the small cell to be controlled.

In an embodiment, the information acquiring unit can judge, based on anuplink signal of a user terminal of the adjacent small cell which hasbeen received by the small cell to be controlled, whether the userterminal is a high-interference user terminal. The uplink signal hereinincludes but is not limited to uplink detecting signal SoundingReference Signal (SRS), PRACH and uplink control or data signalPUSCH/PUCCH. It should be understood that, the function of theinformation acquiring unit 101 can be centralized in the apparatus 100serving as a controller, and can also be distributed in the base stationof each small cell. That is, the base station of each small cellperforms the judgment for the high-interference user terminal, andreports the judgment result to the apparatus 100.

FIG. 5 illustrates the block diagram of an example of the structure ofthe information acquiring unit 101. As shown in FIG. 5, the informationacquiring unit 101 includes: a distance calculating module 1001,configured to calculate a distance from the user terminal of theadjacent small cell to a base station of the small cell to becontrolled; and a judging module 1002, configured to judge the userterminal to be the high-interference user terminal, in the case that apower of the uplink signal is higher than a first predeterminedthreshold, the distance is smaller than the second predeterminedthreshold, and the small cell to be controlled makes use of the samespectrum resources as the user terminal does.

FIG. 6 illustrates an example for calculating the distance d1 betweenthe user terminal UEa and the base station T of the small cell to becontrolled. The user terminal UEa is a user of the base station N of theadjacent small cell and the distance to the base station N is d2.

When using the uplink signal SRS or PRACH, the distance calculatingmodule 1001 is configured to calculate an uplink time advance (TA) fromthe UE to the base station of the small cell to be controlled based onthe SRS or PRACH signal, and estimate the distance according to this TA.For example, in the example of FIG. 6, the distance d1 is calculated tobe 500 m.

If the distance d1 is smaller than the second predetermined threshold(such as 800 m), the uplink signal SRS or PRACH has a power higher thanthe first predetermined threshold, and the small cell to be controlled Tuses the same spectrum resources as the UEa does, it is evaluated thatthe UEa transmitting the uplink signal is subjected to stronginterferences, and thus the judging module 1002 judges the UEa as ahigh-interference UE.

Alternatively, when using the uplink signal PUSCH or PUCCH, the distancecalculating module 1001 is configured to acquire an uplink TA of the UEfrom the base station of its serving small cell, add this TA with a timedeviation between a timing at which the small cell to be controlleddetects the PUSCH/PUCCH signal and an uplink synchronization timing, andtake the resulting sum as an uplink TA from the UE to the base stationof the small cell to be controlled, so as to estimate the distanceaccording to this TA.

Taking FIG. 6 as an example, FIG. 7 illustrates the timing chart for thesignal transmitting and receiving among the small cell base stations T,N and the user terminal UEa. The uplink time advance of UEa is TA1, andit can be calculated that the distance d2 from UEa to the base station Nis 300 m from TA1. The time for the uplink signal PUSCH or PUCCHarriving at the base station N is exactly the uplink synchronizationtiming. The base station T and base station N are synchronized, and thearriving timing of the uplink signal of UEa detected by the base stationN is deviated from the uplink synchronization timing in time, the timedeviation being denoted by T1. As shown in FIG. 7, TA2=TA1+T1, TA2 beingthe uplink time advance from the user terminal UEa to the base stationT, from which it can be calculated that the distance d1 from the UEa tothe base station T is 500 m.

Similarly, if the distance d1 is smaller that the second predeterminedthreshold (such as 800 m), the power of the uplink signal PUSCH or PUCCHis higher than the first predetermined threshold, and the small cell tobe controlled T uses the same spectrum resources as the user terminalUEa does, it is evaluated that the UEa transmitting the uplink signal issubjected to strong interferences, and thus the judging module 1002judges the UEa as a high-interference UE.

The above mentioned first predetermined threshold and the secondpredetermined threshold can be determined according to empirical valueor by experiment.

Although two methods for determining the distance from the user terminalto the base station of the small cell to be controlled are shown above,the method for determining the distance is not limited thereto, andvarious other manners can be adopted. For example, determination can bemade based on the position information of Global Positioning System(GPS), or based on the location information of base stations. Since thetwo methods for determining are known to those skilled in the art, theyare omitted here.

In addition, the method for determining the distance from the userterminal to the base station of the small cell to be controlled based onPUSCH or PUCCCH signal and TA of the user terminal described as anexample above can be applied to various situations requiring to measurea distance, but not limited to the embodiment specifically described inthe application.

In another example, the information acquiring unit 101 can be furtherconfigured to acquire a degree of interference the small cell to becontrolled produced to the adjacent small cell, which is indicated by atleast one of signals of OI (overload indication), HII (high interferenceindication) and RNTP (relative narrowband transmitting power) from theadjacent small cell.

That is, the information acquiring unit 101 can acquire the interferenceindicating signal, i.e., the inter-cell interference coordination signalsuch as OI, HII or RNTP of the X2 interface, to indicate the degree ofinterference the small cell to be controlled produced to the adjacentsmall cell, or receive the degree of interference directly from the basestation of the small cell to be controlled. For example, the OI, HII orRNTP signal sent to the small cell to be controlled by the adjacentsmall cell via a feedback channel (such as the X2 interface) indicatesthat more than 70% of the resources blocks are seriously interfered.

When the information acquiring unit 101 acquires the above mentioneddegree of interference, the state change determining unit 102determines, based on the degree of interference, whether to increase ordecrease the sleep level of the small cell to be controlled by one ormore levels, the levels to be increased or decreased being determinedaccording to the degree of interference.

In one example, the state change determining unit 102 can be configuredto compare the degree of interference with a first threshold and/or asecond threshold which is lower than the first threshold, when thedegree of interference is higher than the first threshold, the statechange determining unit 102 determines to increase the sleep level ofthe small cell to be controlled by one or more levels, and when thedegree of interference is lower than the second threshold, the statechange determining unit 102 determines to decrease the sleep level ofthe small cell to be controlled by one or more levels.

For example, when the degree of interference is higher than the firstthreshold by more than a limit A, it is to increase the sleep level byone level, and when the degree of interference is higher than the firstthreshold by more than a limit B (B>A), it is to increase the sleeplevel by two levels, and so on. Likewise, for example, when the degreeof interference is lower than the second threshold by more than a limitC, it is to decrease the sleep level by one level, and when the degreeof interference is lower than the second threshold by more than a limitD (D<C), it is to decrease the sleep level by two levels, and so on.

In addition, it is also possible to establish the correspondence betweenthe degree of interference and the sleep level. In other words, forexample, when the degree of interference is within a first range, thesmall cell enters into “the small cell base station waking upcompletely”, and when the degree of interference is within a secondrange, the small cell enters into “the sub-frame sleep”, etc, and so on.

In the above, the situation where the information of degree ofinterference the small cell to be controlled produced to the adjacentsmall cell is described. Since the interferences are mutual, theinformation acquiring unit 101 can also acquire information of thedegree of interference the adjacent small cell produced to the smallcell to be controlled. For example, in the case of the user terminal UEabeing a high-interference UE of the base station of the small cell to becontrolled T, the information that the user terminal UEa of the adjacentsmall cell base station N produces high interference to the base stationT is acquired correspondingly in the meantime. For example, the aboveinformation can be acquired for each small cell base station and becollected in the apparatus 100 serving as a controller, so as to obtaina list of a high-interference UE, the base station it belongs to and thebase stations being interfered by it. This list can be stored in theapparatus 100, and can also be stored in a separate database. Based onthis list, small cells producing high interferences to other small cellssuch as small cells whose user terminals produce high interference tomultiple small cell base stations can be searched, and/or small cellssubjected to high interferences from other small cells such as smallcells whose user terminals are high-interference UEs of multipleadjacent small cells can be searched, so that the state changedetermining unit 102 increase the sleep level of these small cellsaccording to the searching result. Specific examples of this list andits application will be described in detail later with reference toFIGS. 20-21.

After the state change determining unit 102 determines the change ofsleep level to be performed, if the apparatus 100 is located in the basestation of the small cell to be controlled, the base station changes itssleep level base don the determined change. If the apparatus 100 is acontrolling apparatus controlling multiple small cell base stations, itis possible to transmit the corresponding control signal to the smallcell to be controlled by the transmitting unit in the apparatus 100, soas to control it to perform the change of the sleep level.

The transmitting of the control signal can use a 1-bit signalrealization scheme. That is, the control signal only occupies 1 bit, andthe 1 bit binary data is used to indicate to increase or decrease thesleep level by one level. For example, 0 denotes increasing by one leveland 1 denotes decreasing by one level.

A N-bit signal realization scheme can also be used. That is, the controlsignal occupies N bits, and the N-bit binary data is used to denote eachoperating state respectively, wherein N>=2. Considering N-bit binarydata can indicate 2^(N) states at most, in the case of setting 6 sleeplevels, N can be 3. For example, 000, 001, 010, 011, 100 and 110 can beallocated to the above mentioned six sleep levels.

The Third Embodiment

In this embodiment, the information acquiring unit 101 is configured toacquire load of the small cell to be controlled or the load to be takenon by the small cell to be controlled which is distributed by othercells. The state change determining unit 102 can determine, based on theload, the change of operation state to be performed by the small cell tobe controlled. Similarly, the information acquiring unit 101 can detectthe above mentioned load by itself, and can also receive the reportabout the load from each small cell base station.

To be noted, although not pointed out explicitly, the informationacquiring unit 101 can further have the configuration described in thefirst embodiment. At this time, the state change determining unit 102can determine the change of operation state to be performed by the smallcell to be controlled based on the acquired interference and/or load. Inother words, the determination can be made based individually on theinterference or individually on the load, and can also be made based onboth the interference and the load.

When there are two factors of the interference and the load, it can bedetermined whether to increase or decrease the sleep level of the smallcell to be controlled by one or more levels based on the interferenceand the load. If the changing trends of the operation state determinedbased on the interference and the load respectively are identical,according to an example of the invention, it is possible to follow theone for which the determined degree of change of the sleep level islarger. For example, if the sleep level of the small cell to becontrolled should be increased by 2 levels based on the load, and thesleep level of the small cell to be controlled should be increased by 3levels based on the interference, it is determined that the sleep levelof the small cell to be controlled is to be increased by 3 levels. Ifthe changing trends of the operation state determined based on theinterference and the load are opposite, in a preferred example of theinvention, the decision based on the load can be followed. Furthermore,it is also possible to perform adjustment based on the conditions of theinterference, on the basis of the decision made according to the load.For example, if the sleep level of the small cell to be controlledshould be decreased by 2 levels based on the load, and the sleep levelof the small cell to be controlled should be increased by 1 level basedon the interference, it is determined that the sleep level of the smallcell to be controlled is to be decreased by only one level.

In an example, the information acquiring unit 101 is configured toacquire load of the small cell to be controlled within a predeterminedtime period, and the state change determining unit 102 is configured todetermine whether to increase or decrease the sleep level of the smallcell to be controlled by one or more levels based on the load, wherein,the number of levels to be decreased or increased is determinedaccording to the conditions of the load. For example, when the load ishigher than a first limit of load, the sleep level is decreased by 1level, and when the load is higher than a second limit of load, thesleep level is decreased by 2 levels, and so on, vice versa.

Specifically, the information acquiring unit 101 cab be configured toacquire the number of user terminals with a high signal-to-noise ratiowhich are served by the small cell to be controlled within thepredetermined time period so as to determine the load, wherein, the userterminals with a high signal-to-noise ratio are the following ones: thesignal-to-noise ratio of an uplink signal which a base station of thesmall cell to be controlled received from the user terminal exceeds apredetermined threshold.

Wherein, the above mentioned uplink signal can be SRS or PRACH signal.Here, the user terminal with a high signal-to-noise ratio denotes theimportant load of the small cell base station. Therefore, it is possibleto evaluate the load conditions of the small cell base station accordingto the number of the user terminals with a high SNR. If the number islarger, it implies that the load of the small cell is higher and it isnecessary to decrease the sleep level thereof. It is possible todirectly set the sleep level to be changed to according to the number,or determine the number of levels to be changed according to the extentthe number exceeding a predetermined value.

In another example, the information acquiring unit 101 is configured toacquire user terminals or carriers to be distributed to the small cellto be controlled from other cells as the load to be distributed, and thestate change determining unit 102 is configured to decrease the sleeplevel of the small cell to be controlled by one or more levels when theload to be distributed exceeds a predetermined amount, and the number oflevels to be decreased depends on the amount of the load to bedistributed.

The “other cells” include both other small cells and macro cells. Themacro cell detects the utilizing ratio of PDSCH resources in severalcarriers thereof. If the utilizing ratio of PDSCH resources in a certaincarrier exceeds a predetermined percentage, such a carrier is a carrierto be distributed. That is, the users in the coverage range of the smallcell to be controlled which use this carrier to communicate can bedistributed to the small cell to be controlled. Therefore, theinformation acquiring unit 101 can be configured to acquire the numberof carriers of a macro cell to be distributed which cover the small cellto be controlled, and when the number exceeds a predetermined value, thestate change determining unit 102 can determine to decrease the sleeplevel of the small cell to be controlled by one or more levels. This isbecause that the small cells covered by more carriers to be distributedof the macro cell can distribute the load of the macro cell moreeffectively.

Specifically, the macro cell can transmit a reference signal on eachcarrier to be distributed, so that the small cell to be controlled candetect the number of received carriers to be distributed by thisreference signal.

FIG. 8 illustrates a structural block diagram of another example of theinformation acquiring unit 101. As shown in FIG. 8, the informationacquiring unit 101 includes: a threshold module 1003, configured tojudge whether an intensity of the uplink signal from the user terminalof the other cells exceeds a predetermined range; a distance calculatingmodule 1004, configured to calculate a distance from the user terminalto a base station of the small cell to be controlled, in the case thatthe intensity of the signal exceeds the predetermined range; and adetermining module 1005, configured to determine, in the case that thedistance is shorter than a predetermined distance, the user terminal tobe the load to be distributed.

The uplink signal can be SRS, PRACH signal or PUSCH, PUCCH signal. Thedistance calculating module 1004 can perform the calculation in the sameway as that of the distance calculating module 1001 described above withreference to FIG. 5 to FIG. 7, which will be omitted here. Further, itis to be noted that although FIG. 8 only illustrates the thresholdmodule 1003, the distance calculating module 1004 and the determiningmodule 1005 for determining the load to be distributed, it can alsoinclude the distance calculating module 1001 and the judging module 1002for judging a high-interference user terminal shown in FIG. 5. Moreover,the output results of the determining module 1005 and the judging module1002 can also be adopted correspondingly in accordance with theprinciple for changing the sleep level in the case of considering bothfactors of interference and load as stated above according torequirement.

Further, FIG. 9 illustrates a structural block diagram of anotherexample of the information acquiring unit 101. Besides each of themodules in FIG. 8, the information acquiring unit 101 further includes acomparing module 1006, configured to compare signal power detected bythe small cell to be controlled from the user terminal with signal powerdetected by the other cells from the user terminal, and the determiningmodule 1005 is further configured to determine, in the case that thesignal power detected by the small cell to be controlled is higher thanthe signal power detected by the other cells, the user terminal to bethe load to be distributed.

In addition, in the case of storing the list of a high-interference UE,the base station it belongs to and the base stations being interfered byit as stated above, small cells producing high interferences to othersmall cells are searched. It can be understood that after increasing thesleep level of such a small cell, the adjacent small cell interfered byit most (for example, with the most high-interference UEs) would becomethe preferred distributing destination to which the base station of thesmall cell releases load. Therefore, when the decision of increasing thesleep level of the small cell is made, it is possible to pre-estimatethe load to be distributed to the adjacent small cell base stationaccording to the decision, and thus determine to decrease the sleeplevel of the adjacent small cell simultaneously.

As described above, in the above example, besides the interference withthe adjacent small cells, it is also possible to determine the change ofoperation state to be performed according to the load conditions of thesmall cell to be controlled, or it is possible to make the determinationbased individually on the load conditions of the small cell to becontrolled.

The Fourth Embodiment

FIG. 10 illustrates a structural block diagram of the apparatus 300 forcontrolling a change of operation state of a small cell according toanother embodiment of the present application. As shown in FIG. 10,besides the information acquiring unit 101 and the state changedetermining unit 102 described with reference to FIG. 2 in the firstembodiment, the apparatus 300 further includes a priority level rankingunit 301, configured to rank, in the case that it is determined thereare multiple small cells to be controlled whose operation state is to bechanged by the state change determining unit 102, priority levels forchanging their state. In addition, although not shown in FIG. 10, theapparatus 300 can further include a transmitting unit.

The priority level ranking unit 301 can be configured to rank inaccordance with conditions such as the load, the interference or thelike of each small cell to be controlled.

Specifically, in one example, the priority level ranking unit 301 isconfigured to rank in accordance with the load of each small cell to becontrolled or the load to be taken on by each small cell to becontrolled which is distributed by other cells, wherein, the smaller theload is, the higher the priority level of increasing the sleep level ofthis small cell to be controlled is, and the larger the load is, thehigher the priority level of decreasing the sleep level of this smallcell to be controlled is.

The load can include the number of users with a high signal to noiseratio, the number of user terminals to be distributed or the number ofcarriers to be distributed as described in the third embodiment and soon, and will not be repeated here. For example, the small cells to becontrolled can be ranked according to the amount of their respectiveload, so as to obtain the priority level ranking for changing the sleeplevel of the small cells to be controlled.

In addition, the priority level ranking unit 301 can be configured torank in accordance with a degree of interference between each small cellto be controlled and its adjacent small cell, wherein, the higher thedegree of interference is, the higher the priority level of increasingthe sleep level of this small cell to be controlled is, and the lowerthe degree of interference is, the higher the priority level ofdecreasing the sleep level of this small cell to be controlled is. Theinterference here includes at least one aspect of the interference thesmall cell to be controlled produced to the adjacent small cell and theinterference the adjacent small cell produced to the small cell to becontrolled.

The degree of interference can include the degree of interferenceindicated by the number of high-interference user terminals, OI, HII, orRNTP signal as described in the second embodiment, and will not berepeated here.

The priority level ranking unit 301 can further be configured to rank inaccordance with a feedback bandwidth or a transmission delay betweeneach small cell to be controlled and a macro cell, wherein, the largerthe feedback bandwidth is or the smaller the transmission delay is, thehigher the priority level of decreasing the sleep level of this smallcell to be controlled is, and the smaller the feedback bandwidth is orthe larger the transmission delay is, the higher the priority level ofincreasing the sleep level of this small cell to be controlled is.

This configuration is based on the idea of firstly choosing basestations with a higher feedback rate or a smaller transmission delay tooperate. Specifically, if the feedback bandwidth between the small cellsand the macro cell can be known when establishing the networksinitially, the priority level ranking is set according to the ranking ofthe feedback bandwidth. Otherwise, each small cell transmits signal tothe macro cell while requesting a reply, and the time interval betweentransmitting the signal and receiving the reply represents thetransmission delay. The priority level ranking is set according to theranking of the delay.

In addition, the priority level ranking unit 301 can be furtherconfigured to rank in accordance with the number of user terminals whichuse the carrier of each small cell to be controlled as the primarycomponent carrier (PCC) and the number of user terminals with doubleconnections of connecting with a base station of a macro cell and withthe small cell to be controlled, wherein, the more the number of userterminals which use the carrier of each small cell to be controlled asthe primary component carrier is, the lower the priority level ofincreasing the sleep level of this small cell to be controlled is, andthe more the number of user terminals with double connections is, thehigher the priority level of increasing the sleep level of this smallcell to be controlled is.

In other words, the larger the number of users using the carrier of thesmall cell to be controlled as the PCC is, the lower the priority levelof making the carrier sleep is. For example, when the number of usersexceeds a certain amount, this carrier of the small cell base station isnot allowed to sleep.

On the other hand, if the number of users within the small cell to becontrolled connecting the base station of the macro cell and the basestation thereof is large, it is possible to consider increasing itssleep level preferentially.

By incorporating the priority level ranking unit 301, in the case ofthere being multiple small cells to be controlled whose sleep level isto be changed, it is possible to perform operation by preferentiallychoosing the small cells to be controlled whose sleep level is mostrequired to be changed according to a certain strategy.

The Fifth Embodiment

FIG. 11 illustrates a structural block diagram of the apparatus 500 forcontrolling a change of operation state of a small cell according toanother embodiment of the present application. As shown in FIG. 11,besides the respective units described with reference to FIG. 10 in thefourth embodiment, the apparatus 400 further includes a batching unit401, configured to change, according to the ranking acquired by thepriority level ranking unit 301, the operation state of each small cellto be controlled in batches, wherein, each unit in said apparatus 400re-perform corresponding operations after the operations state of eachbatch of the small cells to be controlled are changed.

For example, when the state change determining unit 102 determines thereare several such as 50 small cell base stations whose sleep level is tobe increased by one level, and the priority level ranking is performedwith respect to these 50 small cell base stations in accordance with thenumber of high-interference UEs. For example, the sleep control signalcan be transmitted to the first batch of 10 small cell base stations,i.e., the 10 small cell base stations with the most high-interferenceUEs. Thereafter, detecting, ranking and transmitting signalscorrespondingly are performed again. The operations cycle, until nosmall cell base stations requiring changing the sleep level thereofexist.

The Sixth Embodiment

FIG. 12 illustrates a structural block diagram of the apparatus 500 forcontrolling a change of operation state of a small cell according tostill another embodiment of the present application. Besides therespective units described with reference to FIG. 2 in the firstembodiment, the apparatus 500 further includes a request signalreceiving unit 501, configured to receive, from the small cell to becontrolled, a signal requesting to change the operation state thereof.It is to be understood, although not shown in FIG. 12, the apparatus 500can further include the other units described in the fourth and thefifth embodiment as well as the transmitting unit.

In the first embodiment to the fifth embodiment, the apparatus 100, 300and 400 can instruct a small cell to change its sleep level. That is,the apparatus 100, 300 and 400 explores the small cells within itsmanagement range on its own to determine whether there is a small cellwhose sleep level is to be changed. If it determines that there is sucha small cell, that is, the state change determining unit 102 determinesto perform the change of the operation state, it transmits a controlsignal to the related small cell to instruct it to change the operationstate.

However, in this embodiment, it is the small cell who requests to changethe sleep level of itself. In this situation, the small cell acquiresthe interference and load conditions related to itself, and determinewhether it is necessary to change the sleep level. For example, thesmall cell base station is provided with the apparatus 100, 300 or 400.If the small cell considers that it is necessary to change the sleeplevel, it transmits the request signal to the apparatus 500. Preferably,the request signal contains adjusting suggestion of the sleep level, therelevant interference or load conditions. Upon the apparatus 500receives the request signal via the request signal receiving unit 501,it acquires the control signal as stated in the above mentioned firstembodiment to the fifth embodiment, and transmits the control signal tothe above mentioned small cell via the transmitting unit.

Generally speaking, the apparatus 500 can be a separate controllingapparatus, and can also be located in the base station of the clusterheader or the macro cell. The apparatus can control multiple smallcells.

The Seventh Embodiment

The structure and function of the apparatus for controlling the changeof operation state of a small cell have been described above. Theconfiguration of the apparatus for changing operation state of the smallcell on the small cell side will be described with reference to FIG. 13to FIG. 15 below.

As shown in FIG. 13, the apparatus 600 for changing operation state of asmall cell according to an embodiment of the present applicationincludes: a control signal receiving unit 601, configured to receive acontrol signal from the above mentioned apparatus for controlling achange of operation state of a small cell (any one of apparatus 100 and300 to 500, referred as “apparatus for controlling” hereinafter); and astate changing unit 602, configured to change, based on the controlsignal, the operation state of the small cell.

The implementation scheme of the control signal has been described inparticular in the first embodiment, and will not be repeated here. Thestate changing unit 602 changes the sleep level of the small cellaccording to the control signal, for example, increases the sleep levelby one level, changes the sleep level to the sub-frame sleep or thelike.

The Eighth Embodiment

As shown in FIG. 14, besides the units in apparatus 600 described in theseventh embodiment with reference to FIG. 13, the apparatus 700 forchanging operation state of a small cell according to another embodimentof the present application further includes: a request signaltransmitting unit 701, configured to transmit a request signal includingthe change of the operation state to be performed to the apparatus forcontrolling (such as the apparatus 500), wherein, the control signalreceiving unit 601 is configured to receive a control signal which is areply to the request signal from the apparatus for controlling; and thestate changing unit 602 is configured to change, based on the repliedcontrol signal, the operation state of the small cell.

The present embodiment is distinguished from the seventh embodiment inthat, the small cell judges whether to change the operation state atfirst, and then in the case of requiring to change, transmits a requestto the apparatus for controlling. Preferably, the request containsadjusting suggestion of sleep level, relevant interference or loadconditions. The apparatus for controlling uses the relevant interferenceand/or load conditions therein to perform the above mentioned relatedprocessing, and then transmits the obtained controlling signal as thereply to the control signal receiving unit 601. In anotherimplementation, it can be set as follows: when the reply and the requestare identical, it means that the apparatus for controlling permits thechange requested by the small cell; while when the reply and the requestare different from each other, it means that the apparatus forcontrolling corrects the change requested by the small cell, and thesmall cell should perform the change of operation state according to thereceived reply. In addition, if no reply is received, it means that thecontrolling apparatus does not permit change of the operation state, andthe small cell maintains its original operation state.

In this embodiment, the change of operation state to be performedtransmitted by the apparatus 700 can be determined using a componentwith similar functions to the information acquiring unit 101 and thestate change determining unit 102. In other words, the apparatus 700 candetermine the change of operation state to be performed based on theinterference between the small cell it is located in and the adjacentsmall cells, and/or the load of the small cell it is located in or theload to be taken on by the small cell it is located in which isdistributed from other cells. It is to be understood that, the apparatus700 can also adopt other manners to determine the change of operationstate to be performed, and the manners are not limited thereto.

The Ninth Embodiment

As shown in FIG. 15, besides the units in the apparatus 600 describedwith reference to FIG. 13 in the seventh embodiment, the apparatus 800for changing operation state of a small cell according to still anotherembodiment of the present application further includes: a state signaltransmitting unit 801, configured to transmit an indication signalindicating the change of the operation state to the above mentionedapparatus for controlling.

In this embodiment, the small cell can change the sleep level on itsown, and the apparatus 800 report the change performed to the apparatusfor controlling via the state signal transmitting unit 801. At thistime, if the apparatus for controlling does not permit such a change, itcan transmit back a corresponding control signal, and the apparatus 800has to obey the command from the apparatus for controlling.

Similar to the eighth embodiment, in this embodiment, the apparatus 800can determine the change of operation state to be performed using acomponent with similar functions to the information acquiring unit 101and the state change determining unit 102. In other words, the apparatus800 can determine the change of operation state to be performed based onthe interference the small cell it is located in produced to theadjacent small cells, and/or the load of the small cell it is located inor the load to be taken on which is distributed from other cells.Similarly, the apparatus 800 can also adopt other manners to determinethe change of operation state to be performed, and the manners are notlimited thereto.

In addition, although not shown in FIG. 15, the apparatus 600, 700 and800 according to the seventh embodiment to the ninth embodiment canfurther include a component for reporting its current sleep level to theapparatus for controlling.

The Tenth Embodiment

During the description of each of the above mentioned apparatus, a basestation is substantively provided as well. The base station includes oneof the apparatus 100 and 300 to 500 in the first embodiment to the sixthembodiment or one of the apparatus 600 to 800 in the seventh embodimentto the ninth embodiment.

Specifically, the base station of the macro cell or the base station ofthe small cell serving as the cluster header can include one of theapparatus 100 and 300 to 500, and the base station of the normal smallcell can include one of the apparatus 100 and 300 to 800.

The Eleventh Embodiment

It is apparent that some processing or methods are also disclosed in thedescription above on the apparatus for controlling a change of operationstate of a small cell and the apparatus for changing operation state ofa small cell according to embodiments of the present invention. Below,the summary of the methods is described without repeating the detailswhich are already discussed above, however, it should be noted thatalthough disclosed in the description of the apparatus for controlling achange of operation state of a small cell and the apparatus for changingoperation state of a small cell, the methods do not certainly employ orare not certainly executed by the aforementioned components. Forinstance, embodiments of the apparatus for controlling a change ofoperation state of a small cell and the apparatus for changing operationstate of a small cell may be partially or completely achieved byhardware and/or firmware, and the method for controlling a change ofoperation state of a small cell and the method for changing operationstate of a small cell described below may be fully achieved by acomputer-executable program, although the methods may employ thehardware and/or firmware of the apparatus for controlling a change ofoperation state of a small cell and the apparatus for changing operationstate of a small cell.

FIG. 16 shows a flowchart of the method for controlling a change ofoperation state of a small cell according to embodiments of the presentapplication. The method includes: acquiring interferences between thesmall cell to be controlled and an adjacent small cell, and/or load ofthe small cell to be controlled or load to be taken on by the small cellto be controlled which is distributed by other cells (S11); anddetermining, based on the acquired interferences and/or the load, achange of operation state to be performed by the small cell to becontrolled (S12), wherein, the operation state includes multiple sleeplevels from low to high, the small cell to be controlled has a lighterdegree of sleep when it is at a lower sleep level than when it is at ahigher sleep level, the change of operation state being performed amongthe multiple sleep levels.

As stated above, various kinds of settings for the sleep level can beadopted. The settings include but are not limited to the followingexample: the sleep level include small cell base station waking upcompletely, sub-frame sleep, sub-carrier downlink sleep, sub-carrieruplink and downlink sleep, small cell base station downlink sleep andsmall cell base station uplink and downlink sleep.

In step S11, the number of high-interference user terminals in theadjacent small cell can be acquired to determine a degree ofinterference the small cell to be controlled produced to the adjacentsmall cell, wherein, the interferences the high-interference userterminal being subjected to from the small cell to be controlled exceeda predetermined limit.

In an example, in the step S11, whether a user terminal of the adjacentsmall cell is a high-interference user terminal can be judged based onan uplink signal of the user terminal which has been received by thesmall cell to be controlled. The uplink signal can be SRS, PRACH orPUSCH, PUCCH.

Specifically, as shown in FIG. 17, the step S11 can include thefollowing sub-steps: calculating a distance from the user terminal to abase station of the small cell to be controlled (S101); and judging theuser terminal to be the high-interference user terminal, in the casethat a power of the uplink signal is higher than a first predeterminedthreshold, the distance is smaller than the second predeterminedthreshold, and the small cell to be controlled makes use of the samespectrum resources as the user terminal does (S102).

In step S101, when the calculation is performed using the uplink signalSRS or PRACH, an uplink time advance (TA) from the user terminal to thebase station of the small cell to be controlled is calculated based onthe SRS or PRACH, and the distance is estimated according to this timeadvance. While the calculation is performed using the uplink signalPUSCH or PUCCH, an uplink time advance (TA) of the user terminal isobtained from the base station of its serving small cell, this timeadvance is added with a time deviation between a timing at which thesmall cell to be controlled detects the PUSCH/PUCCH signal and an uplinksynchronization timing, and the resulting sum is taken as an uplink timeadvance (TA) from the user terminal to the base station of the smallcell to be controlled, so as to estimate the distance according to thistime advance. The details of this algorithm have been described inparticular in the previous embodiments, and will not be omitted here.

In addition, in the step S11, a degree of interference the small cell tobe controlled produced to the adjacent small cell, which is indicated byat least one of signals of OI, HII and RNTP from the adjacent smallcell, can also be acquired.

As stated above, the detection of the degree of interference can beperformed on the controlling side, and can also be performed on the sideof the base station of the small cell to be controlled and reported tothe controlling side.

Then, in step S12, it can be determined whether to increase or decreasethe sleep level of the small cell to be controlled by one or more levelsbased on the above degree of interference, wherein, the number of levelsto be decreased or increased is determined according to the degree ofinterference.

For example, it is possible to compare the degree of interference with afirst threshold and/or a second threshold which is lower than the firstthreshold, when the degree of interference is higher than the firstthreshold, it is determined to increase the sleep level of the smallcell to be controlled by one or more levels, and when the degree ofinterference is lower than the second threshold, it is determined todecrease the sleep level of the small cell to be controlled by one ormore levels.

In addition, in step S11, it is also possible to acquire load of thesmall cell to be controlled or the load to be taken on by the small cellto be controlled which is distributed by other cells. In step S12, thechange of operation state to be performed by the small cell to becontrolled can be determined based on the acquired load or based on boththe acquired interference and the acquired load.

In step S11, it is possible to acquire load of the small cell to becontrolled within a predetermined time period, and in step S12, it isdetermined, based on the load, whether to increase or decrease the sleeplevel of the small cell to be controlled by one or more levels, wherein,the number of levels to be decreased or increased is determinedaccording to the conditions of the load.

In an example, the number of user terminals with a high signal-to-noiseratio which are served by the small cell to be controlled within thepredetermined time period can be acquired so as to determine the load,wherein, the user terminals with a high signal-to-noise ratio are thefollowing ones: the signal-to-noise ratio of an uplink signal which abase station of the small cell to be controlled received from the userterminal exceeds a predetermined threshold.

In another example, user terminals or carriers to be distributed to thesmall cell to be controlled from other cells can be acquired as the loadto be distributed, and it is determined to decrease the sleep level ofthe small cell to be controlled by one or more levels when the load tobe distributed exceeds a predetermined amount. The number of levels tobe decreased depends on the amount of the load to be distributed. It isto be noted that, the carriers to be distributed stated hereinsubstantively refer to the user terminals using these carriers.

Specifically, the step S11 can include the following sub-steps, as shownin FIG. 18: judging whether an intensity of the uplink signal from theuser terminal of the other cells exceeds a predetermined range (S201);calculating a distance from the user terminal to a base station of thesmall cell to be controlled, in the case that the intensity of thesignal exceeds the predetermined range (S202); and in the case that thedistance is shorter than a predetermined distance (S203), determiningthe user terminal to be the load to be distributed (S204).

The step S11 can further include the following step, which is shown inFIG. 18 in a dashed line block: comparing signal power (i.e., theintensity of the uplink signal) detected by the small cell to becontrolled from the user terminal with signal power detected by theother cells from the user terminal to determine whether the former oneis higher (S205), and in the case that the comparison result is yes andthe above mentioned distance is shorter than a predetermined distance,the user terminal is determined to be the load to be distributed.

The step S11 can further include acquiring the number of carriers of amacro cell to be distributed which cover the small cell to becontrolled, wherein, when a PDSCH resource utilizing ratio of a carrierof the macro cell exceeds a predetermined percentage, this carrier isdetermined to be a carrier to be distributed. In an example, the macrocell can transmit a reference signal on each of the carriers to bedistributed, so that the small cell to be controlled detects the numberof the received carriers to be distributed by this reference signal.

In addition, although not shown in the Figures, the step S11 can furtherinclude each of the sub-steps shown in FIG. 17. Moreover, similarly, thedetection of load can be performed on the controlling side, and can alsobe performed on the side of the base station of the small cell to becontrolled and then reported to the controlling side.

When the operation of the steps S11 and S12 is performed on thecontrolling side, the above mentioned method can further include thefollowing step: transmitting the determined change of operation state asa control signal to the small cell to be controlled, so as to control itto perform the change of operation state (S13), which is shown in FIG.16 in a dashed line block.

Referring back to FIG. 16, the above method can further include a stepS31 which is indicated by a dashed line block: in the case that it isdetermined there are multiple small cells to be controlled whoseoperation state is to be changed, ranking priority levels for changingtheir state. By this step, the small cells to be controlled whoseoperation states are to be changed at first can be selected according toa certain strategy.

In the step S31, ranking can be performed according to at least one ofthe following: the load of each small cell to be controlled or the loadto be taken on by each small cell to be controlled which is distributedby other cells, the degree of interference each small cell to becontrolled produced to its adjacent small cell, the feedback bandwidthor transmission delay between each small cell to be controlled and amacro cell, and the number of user terminals which use the carrier ofeach small cell to be controlled as the primary component carrier andthe number of user terminals with double connections of connecting abase station of a macro cell and the small cell to be controlled.

In the case of ranking according to the above mentioned four aspects,the priority degree for the above mentioned four aspects can be set tobe decreasing in order. Of course, other settings can also be adopted,and the example is not limiting.

As shown by another dashed line block in FIG. 16, the above method canfurther include a step S32: changing, according to the acquired ranking,the operation state of each small cell to be controlled in batches,wherein, each unit in said apparatus re-perform corresponding operationsafter the operations state of each batch of the small cells to becontrolled are changed.

The respective steps of the method for controlling a change of operationstate of a small cell have been described with reference to FIG. 16 toFIG. 18 in the above. The specific details can be with reference to theprevious description for the apparatus. In the following, the method forchanging operation state of a small cell will be briefly described withreference to FIG. 19.

As shown in FIG. 19, the method includes: receiving a control signalfrom the apparatus for controlling (S41); and changing, based on thecontrol signal, the operation state of the small cell to be controlled.The apparatus for controlling can be the above mentioned apparatus forcontrolling a change of operation state of a small cell. In such asituation, the small cell side receives the control signal from theapparatus for controlling passively.

In addition, the method can further include a step S43: transmitting anindication signal indicating the change of the operation state to beperformed to the apparatus for controlling. In such a situation, thesmall cell side detects the change of operation state to be performed byitself at first, transmits the corresponding request signal to theapparatus for controlling, receives a control signal as a reply from theapparatus for controlling, and changes the operation state of the smallcell based on the control signal.

As another example, the method can further include a step S44:transmitting an indication signal indicating the change of operationstate to the apparatus for controlling. In such a situation, the smallcell changes its operation state on its own, transmits the indicationsignal indicating such a change to the apparatus for controlling. If theapparatus for controlling does not permit such a change, it willtransmit a control signal indicating how to change and the small cellshould change the operation state again based on the control signal.

Note that, in the present application, the change of operation state ofthe small cell actually refers to the change of the sleep level of thesmall cell base station, unless specified particularly.

In order to facilitate the understanding of the above method, anexemplary system embodiment is given in the following with reference tothe application scenario of FIG. 1 and the lists in FIG. 20 and FIG. 21,to describe how to implement the method of changing the sleep level ofthe small cell base stations by grading and in batches.

Each small cell base station detects the uplink signal. For example, thesmall cell base station Z detects that the user UEa of the adjacentsmall cell A is a high-interference user. That is, the power of theuplink signal received by the base station Z from the user UEa exceeds acertain value and the distance from UEa to the base station Z (themethod based on the TA measurement described in the previous embodimentcan be adopted.) is shorter than a certain distance, and thus it isjudged that the user UEa is a high-interference user of the base stationZ. Since the interference is mutual, it can also be judged that the userUEa produces high interference to the base station Z. Such kind ofinformation is reported to the apparatus for controlling, therebygenerating the interference list shown in FIG. 20.

As shown in FIG. 20, capital letters A-Z are used to denote small cellbase stations and small cells in the controlling range, and smallletters a-z are used to denote user terminals of the small cells. Theinterference lists shown in FIG. 20 and FIG. 21 can be stored forexample in the above mentioned apparatus for controlling, and can alsobe stored in a separate storage device. Small cells whose sleep level isto be changed are selected using this interference list.

As can be seen from FIG. 20, as a high-interference small cell whoseuser terminals produce high interference to other small cells, A isreported 4 times, B is reported 3 times, C is reported 3 times, D isreported twice, E is reported twice, and F is reported once. The basestation being reported the most times produces most serious interferenceto other small cells, and thus be provided with the highest prioritylevel of increasing the sleep level, i.e., A>B=C>D=E>F. The adjacentbase station subjected to the interference from the base station mostseriously will become the preferred distributing destination to whichthe base station release its load after the base station sleeps.Therefore, when making the decision of increasing the sleep level of thebase station, the distributed load to be taken on by this adjacent basestation can be pre-estimated according to the decision, and thus it canbe determined to decrease the sleep level of the adjacent base stationas well as the priority level of decreasing the sleep level thereofsimultaneously. That is, the base station Z reports about A the mosttimes, and the priority level of decreasing the sleep level of Z ishighest. The base station V reports about B the most times, and thepriority level of decreasing the sleep level of V is the second highest.As so on, the priority level of decreasing sleep level is: Z>V=S>P=M>K.

The scheme of sleep level is changed by grading and in batches. Thesleep level of two base stations is increased and the sleep level of twobase stations is decreased first. The base stations whose sleep level isto be increased is A, B and C, and the base stations whose sleep levelis to be decreased is Z, V and S. It is necessary to compare thepriority level of B, C and V, S. The number of the high-interference UEsof B is more than that of C, and the priority level of increasing thesleep level of B is higher than that of C.

In the case of increasing the sleep level of B and C, V and S which arebase stations subjected to the most serious interferences from them willtake on the same amount of distributed load. Thus, the number ofcarriers to be distributed of the macro cell covering the small cell isfurther compared. At this time, the macro cell has 5 carriers, amongwhich 3 carriers has a PDSCH resource utilization ratio beyond thethreshold and are carriers to be distributed. V receives 3 carriers tobe distributed, and S receives 1 carrier to be distributed. Therefore,the priority level of decreasing the sleep level of V is higher thanthat of S. Consequently, the sleep level of the base stations A and B isincreased and the sleep level of the base stations Z and V is decreased.

For example, the apparatus for controlling can transmit the controlsignal “0” to the base stations A and B, and transmit the control signal“1” to the base stations Z and V. After receiving the control signal,each base station performs the action of increasing the sleep level byone level or decreasing the sleep level by one level correspondingly.

Then, the interference list is detected again. At this time, theinterference list is as shown in FIG. 21. C is reported 3 times, A isreported twice, D is reported twice, E is reported twice, and F isreported once. Therefore, the priority level of increasing the sleeplevel is: C>A=D=E>F, and the priority level of decreasing the sleeplevel is: S>X=P=M>K.

Similarly, according to the scheme of changing the sleep level bygrading and in batches, the sleep level of two base station is increasedand the sleep level of two base stations is decreased first. The basestations whose sleep level is to be increased is C, A, D and E, and thebase stations whose sleep level is to be decreased is S, X, P and M. Itis necessary to compare the priority level of A, D, E and X, P, Mrespectively. The number of the high-interference UEs of B is more thanthat of C, and the priority level of increasing the sleep level of B ishigher than that of C.

The number of high-interference UEs is the same for A, D and E. Further,the number of primary serving cell users, i.e., the number of userswhich use the carrier provided by this cell as the primary componentcarrier, is compared. When the number of users who take the base stationA as a primary cell is 5, the number of users who take the base stationD as a primary cell is 5, and the number of users who take the basestation E as a primary cell is 10, the priority level of increasing thesleep level is C>A=D>E. Then the transmission delay is compared. Whenthe average value of the feedback delay between the base station A andthe adjacent cell is 50 μs, and the average value of the feedback delaybetween the base station D and the adjacent cell is 20 μs, the prioritylevel of increasing the sleep level is C>A>D>E. Therefore, the sleeplevel of the base station C and base station A is increased.

The numbers of high-interference UEs of X, P and M are the same as well.The number of carriers to be distributed of the macro cell covering thesmall cell is further compared. At this time, the macro cell still has 3carriers to be distributed. X receives 3 carriers to be distributed, Preceives 3 carriers to be distributed, and M receives 1 carrier to bedistributed. Therefore, the priority level of decreasing the sleep levelis: S>X=P>M. The number of users with a high signal to noise ratio (SNR)is further compared. The cell X has 30 users with a high SNR therein,and the cell P has 15 users with a high SNR therein. Thus, the prioritylevel of decreasing the sleep level is S>X>P>M. Consequently, the sleeplevel of the base stations S and X is decreased.

The apparatus for controlling transmits the control signal “0” to thebase stations C and A, and transmits the control signal “1” to the basestations S and X. After receiving the control signal, each base stationperforms the action of increasing the sleep level by one level ordecreasing the sleep level by one level correspondingly.

Then, the above mentioned operations are repeated until the interferencelist is empty.

It should be understood that although the system embodiment is describedherein as an example, the specific implementation of the presentapplication is not limited thereto, instead, it can adopt variousmanners described above in each embodiment.

In conclusion, by changing the sleep level of the small cell to becontrolled according to its interference and/or load conditions, theapparatus and method of the present application can reduce the energyconsumption while ensuring the communication quality as much aspossible.

The basic principle of the present invention has been described above inconjunction with particular embodiments. However, as can be appreciatedby those ordinarily skilled in the art, all or any of the steps orcomponents of the method and apparatus according to the invention can beimplemented in hardware, firmware, software or a combination thereof inany computing device (including a processor, a storage medium, etc.) ora network of computing devices by those ordinarily skilled in the art inlight of the disclosure of the invention and making use of their generalcircuit designing knowledge or general programming skills.

Moreover, the present invention further discloses a program product inwhich machine-readable instruction codes are stored. The aforementionedmethods according to the embodiments can be implemented when theinstruction codes are read and executed by a machine.

Accordingly, a memory medium for carrying the program product in whichmachine-readable instruction codes are stored is also covered in thepresent invention. The memory medium includes but is not limited to softdisc, optical disc, magnetic optical disc, memory card, memory stick andthe like.

In the case where the present application is realized by software orfirmware, a program constituting the software is installed in a computerwith a dedicated hardware structure (e.g. the general computer 2200shown in FIG. 22) from a storage medium or network, wherein the computeris capable of implementing various functions when installed with variousprograms.

In FIG. 22, a computing processing unit (CPU) 2201 executes variousprocessing according to a program stored in a read-only memory (ROM)2202 or a program loaded to a random access memory (RAM) 2203 from astorage section 2208. The data needed for the various processing of theCPU 2201 may be stored in the RAM 2203 as needed. The CPU 2201, the ROM2202 and the RAM 2203 are linked with each other via a bus 2204. Aninput/output interface 2205 is also linked to the bus 2204.

The following components are linked to the input/output interface 2205:an input section 2206 (including keyboard, mouse and the like), anoutput section 2207 (including displays such as a cathode ray tube(CRT), a liquid crystal display (LCD), a loudspeaker and the like), astorage section 2208 (including hard disc and the like), and acommunication section 2209 (including a network interface card such as aLAN card, modem and the like). The communication section 2209 performscommunication processing via a network such as the Internet. A driver2210 may also be linked to the input/output interface 2205, if needed.If needed, a removable medium 2211, for example, a magnetic disc, anoptical disc, a magnetic optical disc, a semiconductor memory and thelike, may be installed in the driver 2210, so that the computer programread therefrom is installed in the memory section 2208 as appropriate.

In the case where the foregoing series of processing is achieved throughsoftware, programs forming the software are installed from a networksuch as the Internet or a memory medium such as the removable medium2211.

It should be appreciated by those skilled in the art that the memorymedium is not limited to the removable medium 2211 shown in FIG. 22,which has program stored therein and is distributed separately from theapparatus so as to provide the programs to users. The removable medium2211 may be, for example, a magnetic disc (including floppy disc(registered trademark)), a compact disc (including compact discread-only memory (CD-ROM) and digital versatile disc (DVD), a magnetooptical disc (including mini disc (MD) (registered trademark)), and asemiconductor memory. Alternatively, the memory medium may be the harddiscs included in ROM 2202 and the storage section 2208 in whichprograms are stored, and can be distributed to users along with thedevice in which they are incorporated.

To be further noted, in the apparatus, method and system according tothe invention, the respective components or steps can be decomposedand/or recombined. These decompositions and/or recombinations shall beregarded as equivalent solutions of the invention. Moreover, the aboveseries of processing steps can naturally be performed temporally in thesequence as described above but will not be limited thereto, and some ofthe steps can be performed in parallel or independently from each other.

Finally, to be further noted, the term “include”, “comprise” or anyvariant thereof is intended to encompass nonexclusive inclusion so thata process, method, article or device including a series of elementsincludes not only those elements but also other elements which have beennot listed definitely or an element(s) inherent to the process, method,article or device. Moreover, the expression “comprising a(n) . . . ” inwhich an element is defined will not preclude presence of an additionalidentical element(s) in a process, method, article or device comprisingthe defined element(s)” unless further defined.

Although the embodiments of the invention have been described above indetail in connection with the drawings, it shall be appreciated that theembodiments as described above are merely illustrative but notlimitative of the invention. Those skilled in the art can make variousmodifications and variations to the above embodiments without departingfrom the spirit and scope of the invention. Therefore, the scope of theinvention is defined merely by the appended claims and theirequivalents.

1. An apparatus for controlling a change of an operation state of asmall cell, comprising: circuitry configured to: acquire informationcomprising interferences between the small cell and an adjacent smallcell, and at least one of a first load of the small cell and a secondload to be taken on by the small cell that is distributed by othercells; and compare a first signal power detected by the small cell fromthe user terminal with a second signal power detected by the other cellsfrom the user terminal, when a first signal power detected by the smallcell from the user terminal is higher than a second signal powerdetected by the other cells from the user terminal; the user terminal tobe the second load; base on the information determine the change of theoperation state to be performed by the small cell.
 2. The apparatusaccording to claim 1, wherein the operation state comprises multiplesleep levels from low to high, the small cell being more active when itis at a lower sleep level than when it is at a higher sleep level, andthe change of the operation state is performed among the multiple sleeplevels.
 3. The apparatus according to claim 2, wherein the sleep levelscomprise: (i) a first sleep level during which the small cell basestation waking up completely, and all sub-frames on all carriers of thebase station of small cell are turned on; (ii) a second sleep levelduring which the sub-frame sleep, and a part of sub-frames on thecarriers being turned on are turned off; (iii) a third sleep levelduring which the sub-carrier downlink sleep, and all the downlinksub-frames on a part of carriers of the base station of the small cellare turned off; (iv) a fourth sleep level during which the sub-carrieruplink and downlink sleep, and all the uplink sub-frames and downlinksub-frames on a part of carriers of the base station of the small cellare turned off; (v) a fifth sleep level during which the small cell basestation downlink sleep, and all the downlink sub-frames of the basestation of the small cell are turned off; (vi) a sixth sleep levelduring which the small cell base station uplink and downlink sleep, andall the uplink sub-frames and downlink sub-frames of the base station ofthe small cell are turned off.
 4. The apparatus according to claim 3,wherein the circuitry is further configured to: set the downlink isturned off have more priority in contrast with the uplink; and base onthe levels of sub-carrier downlink sleep and small cell base stationdownlink sleep, turn off the downlink first while the uplink remains. 5.The apparatus according to claim 3, wherein the circuitry is furtherconfigured to: transmit periodic discovery signals when in a secondsleep level during which the sub-frame sleep, and a part of sub-frameson the carriers being turned on are turned off.
 6. The apparatusaccording to claim 3, wherein the circuitry is further configured to:transmit periodic discovery signals when in a fifth sleep level duringwhich the small cell base station downlink sleep, and all the downlinksub-frames of the base station of the small cell are turned off.
 7. Theapparatus according to claim 1, wherein the circuitry is furtherconfigured to: base on an uplink signal of a user terminal of theplurality of user terminals of the adjacent small cell that has beenreceived by the small cell, determine whether the level of interferencethe user terminal is suffered from the small cell exceeds thepredetermined limit.
 8. The apparatus according to claim 7, wherein thecircuitry is further configured to: calculate a distance from the userterminal to a base station of the small cell; and when a power of theuplink signal is higher than a first predetermined threshold, thedistance is smaller than a second predetermined threshold, and the smallcell employ the same spectrum resources as the user terminal, determinethe user terminal to be the high-interference user terminal.
 9. Theapparatus according to claim 1, wherein the circuitry is configured toacquire the first load of the small cell within a predetermined timeperiod, and determine, based on the first load, whether to increase ordecrease the sleep level of the small cell by one or more levels,wherein a number of levels to be decreased or increased is determinedaccording to situations of the first load.
 10. The apparatus accordingto claim 9, wherein the circuitry is further configured to identify auser terminal with a high signal-to-noise ratio that is served by thesmall cell within the predetermined time period to determine the firstload, wherein the user terminal is identified to have the highsignal-to-noise ratio when a signal-to-noise ratio of an uplink signalthat a base station of the small cell received from the user terminalexceeds a predetermined threshold.
 11. The apparatus according to claim1, wherein the circuitry is further configured to identify userterminals or carriers to be distributed to the small cell from the othercells as the second load, and decrease the sleep level of the small cellby one or more levels when the second load exceeds a predeterminednumber, and a number of levels to be decreased depends on an number ofthe second load.
 12. The apparatus according to claim 11, wherein thecircuitry is further configured to: judge whether an intensity of theuplink signal from the user terminal of the other cells exceeds apredetermined range; calculate a distance from the user terminal to abase station of the small cell when the intensity of the uplink signalexceeds the predetermined range; and determine, when the distance isshorter than a predetermined distance, the user terminal to be thesecond load.
 13. The apparatus according to claim 11, wherein thecircuitry is further configured to identify a carrier of a plurality ofcarriers of a macro cell to be distributed that covers the small cell,wherein, when a PDSCH resource utilizing ratio of a carrier of the macrocell exceeds a predetermined percentage, the carrier is determined to bea carrier to be distributed.
 14. The apparatus according to claim 11,wherein the macro cell transmits a reference signal on each of theplurality of carriers, so that the small cell detects a number ofreceived carriers by this reference signal.
 15. The apparatus accordingto claim 1, wherein the circuitry is further configured to transmit thechange of the operation state as a control signal to the small cell, inorder to control the small cell to carry out the change of the operationstate.
 16. The apparatus according to claim 1, wherein the circuitry isfurther configured to: determine that there are multiple small cells tobe controlled whose operation state is to be changed; and rank prioritylevels for changing the operation state of respective ones of themultiple small cells.
 17. The apparatus according to claim 16, whereinthe circuitry is further configured to rank the priority levels forchanging the operation state of respective ones of the multiple smallcells in accordance with at least one of: a load of each of the smallcells or a load to be taken on by each of the small cells, wherein asmaller load corresponds to a higher one of the priority levels ofincreasing the sleep level of the respective one of the small cells, anda larger load corresponds to a higher one of the priority levelsdecreasing the sleep level of the respective one of the small cells; adegree of interference between each small cell and its adjacent smallcell, wherein a higher degree of the interference corresponds to ahigher one of the priority levels of increasing the sleep level of therespective one of the small cells, and a lower degree of theinterference corresponds to a higher one of the priority levels ofdecreasing the sleep level of the respective one of the small cells; afeedback bandwidth or a transmission delay between each respective oneof the multiple small cells and a macro cell, wherein a larger feedbackbandwidth or a smaller transmission delay corresponds to a higher one ofthe priority levels of decreasing the sleep level of the respective oneof the small cells, and a smaller feedback bandwidth or a largertransmission delay corresponds to a higher one of the priority levels ofincreasing the sleep level of the respective one of the small cells; anda number of user terminals that use a carrier of the respective one ofthe small cells as a primary component carrier and a number of userterminals with double connections of connecting with a base station of amacro cell and with the respective one of the small cells, wherein alarger number of the user terminals that use the carrier of therespective one of the small cells as the primary component carriercorresponds to a lower one of the priority levels of increasing thesleep level of the respective one of the small cells, and a largernumber of the user terminals with double connections corresponds to ahigher one of the priority levels of increasing the sleep level of therespective one of the small cells.
 18. A base station, comprising theapparatus according to claim
 1. 19. An method for controlling a changeof an operation state of a small cell, comprising: acquire informationcomprising interferences between the small cell and an adjacent smallcell, and at least one of a first load of the small cell and a secondload to be taken on by the small cell that is distributed by othercells; and compare a first signal power detected by the small cell fromthe user terminal with a second signal power detected by the other cellsfrom the user terminal, when a first signal power detected by the smallcell from the user terminal is higher than a second signal powerdetected by the other cells from the user terminal; the user terminal tobe the second load; base on the information determine the change of theoperation state to be performed by the small cell.